Deformation and failure mechanism of the mudstone slope in Xianfeng open-pit coal mine under rainfall condition

Mudstone is extensively distributed in the open-pit mining area of Xianfeng Coal Mine in Yunnan, China. Since 2018, with the continuous rainfall, mudstone landslide has gradually emerged as a serious issue in the region. However, there are currently scarce research reports on rainfall-induced mudstone landslide. Therefore, this paper takes the northern slope of the Xianfeng Coal Mine as an example. Based on on-site field investigations and real-time monitoring data, the paper, while analyzing the characteristics of slope deformation, elucidates the impact of rainfall and geological lithology on the superficial failure of landslides. Analysis of existing data indicates that during sustained periods of rainfall, the infiltration process of rainwater undergoes a transformation. Initially, a major portion of the rainwater flows along the surface of the slope, while in the later stages, a significant portion of it infiltrates vertically along the slope surface and cracks. Consequently, the mode of slope deterioration also undergoes a transformation. Additionally, under the influence of rainfall infiltration, the mudstone layer at the base of the slope undergoes expansive deformation, resulting in a significant reduction in the shear strength of the slope.